Notation for Human Movement

Spatial positions of various parts of the human body can be described referring to a Cartesian coordinate system that originates at the center of gravity of the human body in the standing configuration (Fig. 1.2). The directions of the coordinate axis indicate the three primary planes of a standing person. The transverse plane is made up of the x1 and x3 axes. It passes through the hip bone and lies at a right angle to the long axis of the body, dividing it into superior and inferior sections. Any imaginary sectioning of the human body that is parallel to the (x1, x3) plane is called a transverse section or cross section.

The frontal plane is the plane that passes through the x1 and x2 axes of the coordinate system (see Fig. 1.2). It is also called the coronal plane. The

Figure 1.2. The three primary planes of a standing person. The sagittal plane is the only plane of symmetry. This plane divides the body into left- and right-hand sides. The frontal plane separates the body into anterior and posterior portions. The transverse (horizontal) plane divides the body into two parts: superior and inferior.

Figure 1.2. The three primary planes of a standing person. The sagittal plane is the only plane of symmetry. This plane divides the body into left- and right-hand sides. The frontal plane separates the body into anterior and posterior portions. The transverse (horizontal) plane divides the body into two parts: superior and inferior.

frontal plane divides the body into anterior and posterior sections. The sagittal plane is the plane made by the x2 and x3 axes. The sagittal plane divides the body into left and right sections. It is the only plane of symmetry in the human body.

Anatomists have also introduced standard terminology to classify movement configurations of the various parts of the human body (Fig. 1.3). Most movement modes require rotation of a body part around an axis that passes through the center of a joint, and such movements are called angular movements. The common angular movements of this type are flexion, extension, adduction, and abduction.

Flexion and extension are movements that occur parallel to the sagittal plane. Flexion is rotational motion that brings two adjoining long bones closer to each other, such as occurs in the flexion of the leg or the forearm. Extension denotes rotation in the opposite direction of flexion; for example, bending the head toward the chest is flexion and so is the motion of bending down to touch the foot. In that case, the spine is said to be flexed. Extension reverses these movements. Flexion at the shoulder and the hip is defined as the movement of the limbs forward whereas extension means movement of the arms or legs backward. Flexion of the wrist moves the palm forward, and extension moves it back. If the movement of extension continues past the anatomical position, it is called hyperextension.

flexion

Figure 1.3a-c. Anatomical notations used in describing the movements of various body parts: abduction and adduction (a), rotation (b), and flexion and extension (c).

flexion

Figure 1.3a-c. Anatomical notations used in describing the movements of various body parts: abduction and adduction (a), rotation (b), and flexion and extension (c).

Abduction and adduction are the movements of the limbs in the frontal plane. Abduction is movement away from the longitudinal axis of the body whereas adduction is moving the limb back. Swinging the arm to the side is an example of abduction. During a pull-up exercise, an athlete pulls the arm toward the trunk of the body, and this movement constitutes adduction. Spreading the toes and fingers apart abducts them. The act of bringing them together constitutes adduction.

Yet another example of angular motion is the movement of the arm in a loop, and this movement is called circumduction. The rotation of a body part with respect to the long axis of the body or the body part is called rotation. The rotation of the head could be to the left or right. Similarly, the forearm and the hand can be rotated to a degree around the longitudinal axis of these body parts.

There are other types of specialized movements such as the gliding motion of the head with respect to the shoulders or the twisting motion of the foot that turns the sole inward. For more information on the anatomical classification of human movement, the reader may consult an anatomy book, some of which have been listed in the references at the end of this volume.

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.